what os - 32 or 64 bit questions

hey what's up. i'm still working on my friend's computer (other thread). i'm assuming it's windows xp pro 32 bit, but how do i tell for sure (32 bit or 64 bit - check screenshots below)? basically, this computer was home built by someone else years ago (for my friend), but when i tried to validate the comp (to do ms updates), it's not a legit copy. so, i am trying to help him find the cheapest copy that i can find, to make him legit. now, what's the difference between "OEM version", and "Full Product" (links below)?

http://www.flickr.com/photo_zoom.gne?id=2093781375&size=o <-- (System Properties)

http://www.flickr.com/photo_zoom.gne?id=2093781377&size=o <-- (Microsoft Validation Message) <-- (149.00)

http://software.pricegrabber.com/windows-family-os/m/471918/search=windows xp pro/sort_type=price <-- ($112.90 - Microsoft Windows XP Professional - OEM - MPN: E8500913)

http://software.pricegrabber.com/wi...earch=windows xp pro/qlty=all/sort_type=price <-- (112.90 - Microsoft Windows XP Professional - Full Product - MPN: E8500086

as stated earlier, this is a custom (home built) computer, and i don't know if i need other drivers that i don't have (or they have). would it help if i ran an "everest report" now (before i consider a clean install)?

1) it has an "ABIT m/b (NF8-V)
2) it's an AMD Sempron(tm) Processor 3000+, 1.81 GHz, 512 MB of RAM
3) some of the software i'm not sure about, from add/remove programs (screenshots below):
4) i'm not concerned about the printer and camera stuff, just drivers for the m/b, video drivers, etc.

http://www.flickr.com/photo_zoom.gne?id=2093837391&size=o <-- has a program (amd athlon 64 processor driver)
http://www.flickr.com/photo_zoom.gne?id=2093837393&size=o
http://www.flickr.com/photo_zoom.gne?id=2093837395&size=o
http://www.flickr.com/photo_zoom.gne?id=2093837399&size=o
http://www.flickr.com/photo_zoom.gne?id=2093837401&size=o
http://www.flickr.com/photo_zoom.gne?id=2093837407&size=o

i have done a few reinstallations, and have had no major problems (for the most part). but i have run into (no sound), due to not having onboard sound drivers. that was an easy fix, as i sold a sblive card (brand new in the box for $25) to an ex-manager of mine, and all was good (no charge for installation), and i never even charged her for backing up her comp, and reinstalling her os. anyway, i'm leary on this one, so i'd appreciate any and all feedback. sorry, for so many questions, but i know i can count on you peeps (guys/gals). thx, sos :major